1. Field of the Invention
This invention relates to centrifugal pumps, and more particularly, it relates to improvements therein for securing the impeller upon the pump shaft.
2. Description of the Prior Art
Centrifugal pumps are very useful machines and they have been used for many years in moving fluids. The centrifugal pumps have a casing forming a chamber with fluid inlet and outlet. An impeller is positioned in the chamber and rotated by a pump shaft. The pump shaft can be a part of a motor shaft or a separate shaft carried in its own bearing journals. In large centrifugal pumps, the separate pump shaft is usually employed. Various arrangements are used to secure the impeller to the pump shaft, but in any event, the impeller cannot move axially in the close confines of the chamber. Otherwise, injury to the casing and impeller will occur.
In some arrangements, the impeller directly, or by an integral nut, threads upon the end of the pump shaft of the centrifugal pump. When the pump shaft suffers reverse rotation, the impeller attempts to spin-off the pump shaft. However, the axial clearance is usually less than one-eighth inch between the impeller and casing. As a result, the impeller jams against the casing and is held against rotation relative to the spinning pump shaft. Now, the continued unthreading of the impeller on the pump shaft can force the pump shaft axially away from the casing. Usually, the pump shaft is forced from the casing and the bearing journals. Either of these results causes serious injury to the system.
It has been proposed to prevent the problems in centrifugal pumps from undesired reverse rotation of the pump shaft. For example, counterdirectional threading sleeves and shaft nuts have been designed to avoid this problem, e.g., see U.S. Pat. No. 3,904,301 which issued Sept. 9, 1975. However, these multi-thread locking systems are complex, expensive, require special machined parts and are not compatible with conventional pump shafts and impellers.
The present invention provides an improved centrifugal pump impeller attachment usuable with most conventional pump designs that does not require complex mechanical constructions. Further, this attachment provides a fail safe release of the impeller from the pump shaft so that reverse rotation accidents cannot cause injury to any part of the centrifugal pump.